U.S. patent number 9,252,335 [Application Number 13/770,308] was granted by the patent office on 2016-02-02 for semiconductor light emitting element and method for manufacturing same.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba. The grantee listed for this patent is Kabushiki Kaisha Toshiba. Invention is credited to Yuko Kato, Eiji Muramoto, Yasuharu Sugawara.
United States Patent |
9,252,335 |
Sugawara , et al. |
February 2, 2016 |
Semiconductor light emitting element and method for manufacturing
same
Abstract
According to one embodiment, a semiconductor light emitting
element includes a conductive substrate, a bonding portion, an
intermediate metal film, a first electrode, a semiconductor stacked
body and a second electrode. The bonding portion is provided on the
support substrate and including a first metal film. The
intermediate metal film is provided on the bonding portion and
having a larger linear expansion coefficient than the first metal
film. The first electrode is provided on the intermediate metal
film and includes a second metal film having a larger linear
expansion coefficient than the intermediate metal film. The
semiconductor stacked body is provided on the first electrode and
including a light emitting portion. The second electrode is
provided on the semiconductor stacked body.
Inventors: |
Sugawara; Yasuharu (Kanagawa,
JP), Kato; Yuko (Kanagawa, JP), Muramoto;
Eiji (Kanagawa, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba |
Tokyo |
N/A |
JP |
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Assignee: |
Kabushiki Kaisha Toshiba
(Tokyo, JP)
|
Family
ID: |
44530546 |
Appl.
No.: |
13/770,308 |
Filed: |
February 19, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130164866 A1 |
Jun 27, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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12878967 |
Sep 9, 2010 |
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Foreign Application Priority Data
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Mar 5, 2010 [JP] |
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2010-049418 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
33/48 (20130101); H01L 33/40 (20130101); H01L
33/62 (20130101); H01L 33/54 (20130101); H01L
33/36 (20130101); H01L 33/405 (20130101); H01L
33/38 (20130101); H01L 2224/48247 (20130101); H01L
2224/48091 (20130101); H01L 2224/48091 (20130101); H01L
2924/00014 (20130101) |
Current International
Class: |
H01L
33/40 (20100101); H01L 33/62 (20100101); H01L
33/48 (20100101); H01L 33/36 (20100101); H01L
33/38 (20100101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2007-251112 |
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Sep 2007 |
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JP |
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2008186959 |
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Aug 2008 |
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JP |
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2009-054693 |
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Mar 2009 |
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JP |
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2009-099675 |
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May 2009 |
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JP |
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2010-016055 |
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Jan 2010 |
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JP |
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2011-077190 |
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Apr 2011 |
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JP |
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Other References
Japanese Office Action dated Sep. 9, 2013, filed in Japanese
counterpart Application No. 2012-168642. cited by applicant .
Lide et al., CRC Handbook of Chemistry and Physics, 80th Edition.
CRC Press, LLC., 1999, pp. 12-193 to 12-194. cited by applicant
.
Japanese Office Action dated Dec. 27, 2011, in Japanese counterpart
application No. 2010-049418. 8 pages (Including English
Translation). cited by applicant .
Japanese Office Action dated May 25, 2012, in Japanese counterpart
application No. 2010-049418. 10 pages (Including English
Translation). cited by applicant .
Japanese Office Action dated Dec. 8, 2014, filed in Japanese
counterpart Application No. 2013-256911, 12 pages (with
translation). cited by applicant .
Japanese Office Action dated Apr. 2, 2015, filed in Japanese
counterpart Application No. 2013-256911, 4 pages (with
translation). cited by applicant.
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Primary Examiner: Chen; Yu
Attorney, Agent or Firm: Patterson & Sheridan, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. patent application Ser.
No. 12/878,967, filed on Sep. 9, 2010, which is based upon and
claims the benefit of priority from the prior Japanese Patent
Application No. 2010-049418, filed on Mar. 5, 2010; the entire
contents of which are incorporated herein by reference.
Claims
The invention claimed is:
1. A semiconductor light emitting element comprising: a support
substrate; a semiconductor stacked body including a light emitting
portion, the semiconductor stacked body having a first surface and
a second surface opposite to the first surface; a first electrode
provided between the second surface and the support substrate; a
bonding portion provided between the first electrode and the
support substrate; and a film covering a side surface of the
semiconductor stacked body, the bonding portion covering the first
electrode, the bonding portion being in contact with the support
substrate, the bonding portion including a first portion and a
second portion the first portion provided between the first
electrode and the second portion, the first portion extending
beyond an outer edge of the second portion in a first direction
that is parallel to the second surface, the first portion having a
third surface that is parallel to the second surface, and the
semiconductor stacked body and the film each having a portion
contacting the first portion along the third surface.
2. The semiconductor light emitting element according to claim 1,
wherein the first electrode has a first film being made of metal,
the first portion of the bonding portion includes: a second film
being made of metal, the second film being in contact with the
second surface, the second film having a linear expansion
coefficient smaller than a linear expansion coefficient of the
first film; and a third film being made of metal, the third film
provided between the second film and the support substrate, the
third film having a linear expansion coefficient smaller than a
linear expansion coefficient of the second film.
3. The semiconductor light emitting element according to claim 2,
wherein the second film includes an intermediate metal film, the
intermediate metal film being in contact with the first film, and
the intermediate metal film being made of one selected from Ni, Pt,
Rh, and Pd.
4. The semiconductor light emitting element according to claim 2,
wherein the first film includes Ag, and the third film includes
Ti.
5. The semiconductor light emitting element according to claim 1,
wherein the side surface of the semiconductor stacked body is
inclined to a plane which is orthogonal to the third surface.
6. The semiconductor light emitting element according to claim 1,
wherein the first surface has a surface area in a first plane
parallel to the third surface that is smaller than a surface area
of the second surface in a second plane parallel to the third
surface.
7. The semiconductor light emitting element according to claim 1,
wherein a length in the first direction of the first portion of the
bonding portion along the third surface is greater than a length in
the first direction of the portion of the semiconductor stacked
body along the third surface.
8. A semiconductor light emitting device, comprising: a
semiconductor light emitting element; a molded body enclosing the
semiconductor light emitting element; and a terminal being in
electrical continuity with the semiconductor light emitting
element, the terminal provided outside the molded body, the
semiconductor light emitting element including: a support
substrate; a semiconductor stacked body including a light emitting
portion, the semiconductor stacked body having a first surface and
a second surface opposite to the first surface; a first electrode
provided between the second surface and the support substrate; a
bonding portion provided between the first electrode and the
support substrate; and a film covering a side surface of the
semiconductor stacked body, the bonding portion covering the first
electrode, the bonding portion being in contact with the support
substrate, the bonding portion including a first portion and a
second portion the first portion provided between the first
electrode and the second portion, the first portion extending
beyond an outer edge of the second portion in a first direction
that is parallel to the second surface, the first portion having a
third surface that is parallel to the second surface, and the
semiconductor stacked body and the film each having a portion
contacting the first portion along the third surface.
Description
FIELD
Embodiments described herein relate generally to a semiconductor
light emitting element and a method for manufacturing the same.
BACKGROUND
Recently, semiconductor light emitting elements with a sandwich
electrode structure have been drawing attention. In this structure,
the light emitting element is sandwiched between electrodes above
and below the element. For instance, an LED (light emitting diode)
is a typical example of such light emitting elements. A
manufacturing process therefor is as follows. On a growth substrate
made of sapphire, for instance, a semiconductor stacked body
including a light emitting portion is formed. Next, a conductive
substrate is bonded to a major surface of the semiconductor stacked
body on the opposite side from the growth substrate. Then, the
growth substrate is removed from the semiconductor stacked body. An
electrode is formed on the surface of the semiconductor stacked
body exposed by the removal of the growth substrate. Another
electrode is formed on the conductive substrate.
With regard to the aforementioned process, a laser lift-off method
has been proposed as a method for removing the growth substrate
from the semiconductor stacked body. However, if the laser lift-off
method is used to remove the growth substrate from the
semiconductor stacked body, peeling may occur at the interface
between the electrode of the semiconductor stacked body and the
bonding portion, the bonding portion being interposed between the
electrode and the conductive substrate. In this context, there is
demand for improving the reliability and manufacturing yield of
semiconductor light emitting elements.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic cross-sectional view describing an example
structure of a semiconductor light emitting element according to a
first embodiment;
FIG. 2 is a schematic cross-sectional view describing an example
structure of a semiconductor light emitting element according to a
comparative example;
FIG. 3 is a schematic cross-sectional view describing an example
configuration of the principal part of the semiconductor light
emitting element according to the first embodiment;
FIGS. 4A to 6C are schematic cross-sectional views sequentially
describing an example process for manufacturing a semiconductor
light emitting element;
FIG. 7 is a schematic cross-sectional view describing part of a
process for manufacturing the semiconductor light emitting element
according to the comparative example;
FIGS. 8A and 8B are schematic cross-sectional views describing an
example structure of a semiconductor light emitting element
according to a third embodiment;
FIGS. 9A to 11D are schematic cross-sectional views sequentially
describing an example process for manufacturing a semiconductor
light emitting element; and
FIG. 12 is a schematic cross-sectional view describing an example
configuration of a semiconductor light emitting device according to
a fifth embodiment.
DETAILED DESCRIPTION
In general, according to one embodiment, a semiconductor light
emitting element includes a conductive substrate, a bonding
portion, an intermediate metal film, a first electrode, a
semiconductor stacked body and a second electrode. The bonding
portion is provided on the conductive substrate and including a
first metal film. The intermediate metal film is provided on the
bonding portion and having a larger linear expansion coefficient
than the first metal film. The first electrode is provided on the
intermediate metal film and includes a second metal film having a
larger linear expansion coefficient than the intermediate metal
film. The semiconductor stacked body is provided on the first
electrode and including a light emitting portion. The second
electrode is provided on the semiconductor stacked body.
Embodiments of the invention will now be described with reference
to the drawings.
The drawings are schematic or conceptual. The relationship between
the thickness and the width of each portion, and the size ratio
between the portions, for instance, are not necessarily identical
to those in reality. Furthermore, the same portion may be shown
with different dimensions or ratios depending on the figures.
In the specification and the drawings, the same components as those
described previously with reference to earlier figures are labeled
with like reference numerals, and the detailed description thereof
is omitted as appropriate.
First Embodiment
FIG. 1 is a schematic cross-sectional view describing an example
structure of a semiconductor light emitting element according to a
first embodiment.
As shown in FIG. 1, the semiconductor light emitting element 110
according to the first embodiment includes a support substrate (a
conductive substrate) 70, a bonding portion 40 provided on the
support substrate 70, an intermediate metal film 50 provided on the
bonding portion 40, a first electrode 30 provided on the
intermediate metal film 50, a semiconductor stacked body 10
provided on the first electrode 30, and a second electrode 20
provided on the semiconductor stacked body 10.
The support substrate 70 is a substrate of a semiconductor such as
silicon (Si) or germanium (Ge). Alternatively, the support
substrate 70 may be made of a metal such as copper (Cu), molybdenum
(Mo), or an alloy containing such metals.
The bonding portion 40 is a member bonding the semiconductor
stacked body 10 to the support substrate 70. The bonding portion 40
includes a first bonding layer 41 previously provided on the first
electrode 30 side, and a second bonding layer 42 previously
provided on the support substrate 70 side. The bonding portion 40
is a bonded structure of the first bonding layer 41 and the second
bonding layer 42. Hence, the first bonding layer 41 and the second
bonding layer 42 may be either integrated together in the bonded
state, or partly integrated, at the boundary therebetween.
The first bonding layer 41 is illustratively a metal multilayer
film including a bonding metal film 411 (a first metal film in the
semiconductor light emitting element), a bonding metal film 412,
and a bonding metal film 413 stacked in this order from the first
electrode 30 side. The bonding metal film 411 is illustratively
made of Ti. The bonding metal film 412 is illustratively made of
Pt. The bonding metal film 413 is illustratively made of Au.
The second bonding layer 42 is illustratively a metal multilayer
film including a bonding metal film 421, a bonding metal film 422,
and a bonding metal film 423 stacked in this order from the support
substrate 70 side. The bonding metal film 421 is illustratively
made of Ti. The bonding metal film 422 is illustratively made of
Pt. The bonding metal film 423 is illustratively made of Au.
The first electrode 30 is provided on a second major surface 10b of
the semiconductor stacked body 10 on the opposite side from its
first major surface 10a. The first electrode 30 is illustratively a
p-side main electrode of the semiconductor light emitting element
110. The first electrode 30 is illustratively a metal multilayer
film. The first electrode 30 illustrated in FIG. 1 is a metal
multilayer film including an electrode metal film 310 and an
electrode metal film 320 (a second metal film in the semiconductor
light emitting element) stacked in this order from the second major
surface 10b of the semiconductor stacked body 10.
The electrode metal film 310 is illustratively made of Ni. The
electrode metal film 310 provides ohmic contact with the
semiconductor stacked body 10. The electrode metal film 320 is
illustratively made of Ag. The electrode metal film 320 serves for
electrical continuity with the electrode metal film 310. In
addition, the electrode metal film 320 also functions as a
reflective film for reflecting light emitted from the light
emitting portion of the semiconductor stacked body 10.
The semiconductor stacked body 10 is illustratively an LED (light
emitting diode). The semiconductor stacked body 10 includes a light
emitting portion provided between the first semiconductor layer and
the second semiconductor layer. By way of example, the light
emitting portion has an MQW (multi-quantum well) structure of
In.sub.0.15Ga.sub.0.85N/In.sub.0.02Ga.sub.0.98N. Blue color or
violet color, for instance, is emitted from the light emitting
portion.
The second electrode 20 is provided on at least part of the first
major surface 10a of the semiconductor stacked body 10. The second
electrode 20 is illustratively an n-side main electrode of the
semiconductor light emitting element 110. The second electrode 20
is illustratively made of conductive film such as ITO (indium in
oxide) or metal film. Alternatively, the second electrode 20 is
illustratively made of a stacked body of AuGe/Mo/Au stacked in this
order, a stacked body of Ti/Pt/Au stacked in this order, or a
stacked body of Cr/Ti/Au stacked in this order from the first major
surface 10a of the semiconductor stacked body 10. In the case of
using ITO or a translucent metal film for the second electrode 20,
light emitted from the semiconductor stacked body 10 can be
extracted outside also from the electrode 20 side.
In the semiconductor light emitting element 110, an intermediate
metal film 50 is provided between the electrode metal film 320 of
the first electrode 30 and the bonding metal film 411 of the
bonding portion 40 (first bonding layer 41). The linear expansion
coefficient of the intermediate metal film 50 is smaller than the
linear expansion coefficient of the electrode metal film 320, and
larger than the linear expansion coefficient of the bonding metal
film 411. The intermediate metal film 50 is illustratively made of
Ni.
A protective film 60 is formed so as to cover a part of the first
major surface 10a, a side surface of the semiconductor stacked body
10, a side surface of the first electrode 30, a side surface of the
intermediate metal film 50, a side surface of the first bonding
layer 41, and a part of upper surface of the second bonding layer
42.
In the semiconductor light emitting element 110, the intermediate
metal film 50 as described above enhances adhesion between the
first electrode 30 and the bonding portion 40 (first bonding layer
41). This suppresses peeling at the interface between the first
electrode 30 and the bonding portion 40 when performing laser
lift-off.
FIG. 2 is a schematic cross-sectional view describing an example
structure of a semiconductor light emitting element according to a
conventional example.
As shown in FIG. 2, the semiconductor light emitting element 190
according to the comparative example includes a support substrate
70, a bonding portion 40 provided on the support substrate 70, a
first electrode 30 provided on the bonding portion 40, a
semiconductor stacked body 10 provided on the first electrode 30,
and a second electrode 20 provided on the semiconductor stacked
body 10.
In the semiconductor light emitting element 190, the electrode
metal film 320 of the first electrode 30 is directly bonded to the
bonding metal film 411 of the first bonding layer 41 in the bonding
portion 40. In contrast, the semiconductor light emitting element
110 includes an intermediate metal film 50 interposed therebetween.
In this point, the semiconductor light emitting element 190 is
different from the semiconductor light emitting element 110.
In the semiconductor light emitting element 190, because the
electrode metal film 320 of the first electrode 30 is directly
bonded to the bonding metal film 411 of the bonding portion 40, it
is difficult to achieve sufficient bonding strength between the
electrode metal film 320 and the bonding metal film 411. Hence,
peeling may occur at the interface between the electrode metal film
320 and the bonding metal film 411 when the growth substrate is
removed by laser lift-off.
In the semiconductor light emitting element 110 according to the
first embodiment, an intermediate metal film 50 is provided between
the electrode metal film 320 and the bonding metal film 411. In
this configuration, the linear expansion coefficient difference
between the electrode metal film 320 and the intermediate metal
film 50, and the linear expansion coefficient difference between
the intermediate metal film 50 and the bonding metal film 411, are
smaller than the linear expansion coefficient difference between
the electrode metal film 320 and the bonding metal film 411.
Adhesion strength between metal films is higher for a smaller
linear expansion coefficient difference between the metal films.
Hence, adhesion strength between metal films from the electrode
metal film 320 to the bonding metal film 411 is higher in the
semiconductor light emitting element 110 according to this
embodiment than in the semiconductor light emitting element 190
according to the comparative example. Thus, separation at the
interface between the electrode metal film 320 and the bonding
metal film 411 is suppressed when the growth is removed by laser
lift-off.
FIG. 3 is a schematic cross-sectional view describing an example
configuration of the principal part of the semiconductor light
emitting element according to the first embodiment.
FIG. 3 primarily illustrates an example configuration of the
semiconductor stacked body 10, the first electrode 30, and the
bonding portion 40.
The first electrode 30 is a multilayer metal film including
electrode metal films 310 and 320 stacked in this order from the
second major surface 10b of the semiconductor stacked body 10.
The bonding portion 40 is a bonded structure of the first bonding
layer 41 and the second bonding layer 42. The first bonding layer
41 is a multilayer metal film including bonding metal films 411,
412, and 413 stacked in this order from the first electrode 30
side.
As described earlier, the linear expansion coefficient of the
intermediate metal film 50 lies between the linear expansion
coefficient of the electrode metal film 320 and the linear
expansion coefficient of the bonding metal film 411.
Here, the linear expansion coefficient of Ag used for the electrode
metal film 320 is 19.1.times.10.sup.-6/.degree. C. The linear
expansion coefficient of Ti used for the bonding metal film 411 is
8.9.times.10.sup.-6/.degree. C.
Besides Ni, the intermediate metal film 50 can illustratively be
made of one selected from Pt, Rh, and Pd.
Here, the linear expansion coefficient of Ni is
13.3.times.10.sup.-6/.degree. C. The linear expansion coefficient
of Pt is 8.98.times.10.sup.-6/.degree. C. The linear expansion
coefficient of Rh is 9.6.times.10.sup.-6/.degree. C. The linear
expansion coefficient of Pd is 10.6.times.10.sup.-6/.degree. C. Any
of these linear expansion coefficients lies between the linear
expansion coefficient of the electrode metal film 320 and the
linear expansion coefficient of the bonding metal film 411. This
decreases the linear expansion coefficient difference of metal
films between the first electrode 30 and the first bonding layer
41, thereby enhancing adhesion strength.
The film thickness d1 of the intermediate metal film 50 may be
larger than the film thickness d2 of the electrode metal film 310
(third metal film) of the first electrode 30. For instance, the
film thickness d2 of the electrode metal film 310 is illustratively
1 nanometer (nm). On the other hand, the film thickness d1 of the
intermediate metal film 50 is illustratively 50 nanometers (nm) or
more and 150 nm or less. The film thickness d2 of the electrode
metal film 310 is set to a thickness such as to transmit of light
into the electrode metal film 320 used as a reflective film. On the
other hand, the film thickness d1 of the intermediate metal film 50
is set to a thickness such as to relax stress between the electrode
metal film 320 and the bonding metal film 411.
In the case of using GaN for the semiconductor stacked body 10, the
intermediate metal film 50 serves to suppress diffusion of Ga from
the semiconductor stacked body 10 into the bonding portion 40.
Diffusion of Ga into the bonding portion 40 decreases bonding
strength in the bonding portion 40. The intermediate metal film 50
suppresses the diffusion of Ga into the bonding portion 40, and
hence can prevent the decrease of adhesion between the first
electrode 30 and the bonding portion 40 (first bonding layer
41).
In view of sufficiently developing the function of suppressing the
diffusion of Ga, it is desirable that the film thickness d1 of the
intermediate metal film 50 be thicker than the film thickness d2 of
the electrode metal film 310.
The electrode metal film 310 is illustratively made of the same
material as the intermediate metal film 50. The electrode metal
film 310 illustrated in FIG. 3 is made of the same material, e.g.
Ni, as the intermediate metal film 50.
In the case of using Ag for the electrode metal film 320, the
intermediate metal film 50 suppresses penetration of the first
bonding layer 41 by Ag constituting the electrode metal film 320.
This prevents the decrease of bonding strength between the first
electrode 30 and the first bonding layer 41.
Second Embodiment
An example method for manufacturing a semiconductor light emitting
element according to a second embodiment is described.
FIGS. 4A to 6C are schematic cross-sectional views sequentially
describing an example process for manufacturing a semiconductor
light emitting element 110.
In this embodiment, a substrate illustratively made of sapphire is
used as a growth substrate 80 for growing a semiconductor stacked
body 10.
First, as shown in FIG. 4A, a semiconductor stacked body 10 is
formed on the growth substrate 80. The thickness of the growth
substrate 80 is illustratively 300-500 micrometers (.mu.m). The
semiconductor stacked body 10 is formed on the growth substrate 80
by epitaxial growth.
Next, a first electrode 30 is formed on the semiconductor stacked
body 10. The first electrode 30 is illustratively a multilayer
metal film of electrode metal films 310 and 320 (a first metal film
in the manufacturing method). Subsequently, an intermediate metal
film 50 is formed on the first electrode 30. Furthermore, a first
bonding layer 41 is formed on the intermediate metal film 50. The
first bonding layer 41 is illustratively a multilayer metal film of
bonding metal films 411 (a second metal film in the manufacturing
method), 412, and 413. The first electrode 30, the intermediate
metal film 50, and the first bonding layer 41 are formed by
sputtering or CVD (chemical vapor deposition), for instance.
Next, as shown in FIG. 4B, the semiconductor stacked body 10, the
first electrode 30, the intermediate metal film 50, and the first
bonding layer 41 are selectively etched and divided on the growth
substrate 80. The division is performed for each chip. By way of
example, FIG. 4B shows a divided state corresponding to three
chips. The etching process may be either dry etching or we etching.
Alternatively, the division may be performed by laser
processing.
Next, as shown in FIG. 4C, a support substrate 70 with a second
bonding layer 42 provided thereon is prepared. Then, the second
bonding layer 42 is brought into face-to-face contact with the
first bonding layer 41. Thus, the semiconductor stacked body 10,
the first electrode 30, the intermediate metal film 50, and the
bonding portion 40 (first bonding layer 41, second bonding layer
42) are sandwiched between the growth substrate 80 and the support
substrate 70.
Then, heating treatment or ultrasonic treatment is performed to
cause interdiffusion between the first bonding layer and the second
bonding layer 42, thereby bonding them together. More specifically,
with the first bonding layer 41 and the second bonding layer 42
opposed to each other, a load of e.g. 5 kgf/cm.sup.2 or more and
500 kgf/cm.sup.2 or less is applied thereto, and they are heated to
e.g. 200.degree. C. or more and 400.degree. C. or less. This causes
interdiffusion between the first bonding layer 41 and the second
bonding layer 42, thereby forming a bonding portion 40. Thus, the
semiconductor stacked body 10 and the support substrate 70 are
bonded. The support substrate 70 also functions as a heat sink, for
instance. Here, the first electrode 30 and the intermediate metal
film 50 are interposed between the semiconductor stacked body 10
and the bonding portion 40.
Next, as shown in FIG. 5A, laser lift-off (LLO) is performed to
remove the growth substrate 80 from the semiconductor stacked body
10. Laser light 75 is produced using, for instance, an ArF laser
(wavelength 193 nm), KrF laser (wavelength 248 nm), XeCl laser
(wavelength 308 nm), or XeF laser (wavelength 353 nm).
The laser light 75 is transmitted through the growth substrate 80
to the semiconductor stacked body 10. Here, at the interface
between the growth substrate 80 and the semiconductor stacked body
10, the semiconductor stacked body 10 absorbs the energy of the
laser light 75. Thus, the III-V nitride components e.g. GaN in the
semiconductor stacked body 10 is thermally decomposed as shown in
the following reaction formula. GaN.fwdarw.Ga+1/2N.sub.2.uparw.
Consequently, as shown in FIG. 5B, the growth substrate 80 is
removed from the semiconductor stacked body 10.
FIG. 7 is a schematic cross-sectional view describing part of a
process for manufacturing the semiconductor light emitting element
190 according to the comparative example.
FIG. 7 shows an example situation in which the same laser lift-off
as in FIG. 5B is performed in the process for manufacturing the
semiconductor light emitting element 190 according to the
comparative example.
In the comparative example, the first electrode 30 is directly
bonded to the first bonding layer 41. Because the intermediate
metal film 50 used in this embodiment is not interposed, adhesion
strength between the first electrode 30 and the first bonding layer
41 may be insufficient. For instance, between the first electrode
30 and the first bonding layer 41, stress has been accumulated by
thermal history during bonding and laser lift-off. This stress
causes the decrease of adhesion strength between the first
electrode 30 and the first bonding layer 41.
If the growth substrate 80 in this state is removed by laser
lift-off, peeling may occur between the first electrode 30 and the
first bonding layer 41. This results in decreasing the reliability
and manufacturing yield of the semiconductor light emitting element
190.
In contrast, as shown in FIG. 5B, in the manufacturing process
according to this embodiment, the intermediate metal film 50 is
provided between the first electrode 30 and the first bonding layer
41. Hence, there is a sufficient adhesion strength between the
first electrode 30 and the first bonding layer 41. That is, because
the intermediate metal film 50 is provided between the first
electrode 30 and the first bonding layer 41, accumulation of stress
due to thermal history during bonding and laser lift-off can be
suppressed. Thus, a sufficient adhesion strength is maintained
between the first electrode 30 and the first bonding layer 41.
This adhesion strength is sufficiently higher than the adhesion
strength between the growth substrate 80 and the semiconductor
stacked body 10 after irradiation with laser light 75. Hence, when
the growth substrate 80 is removed by laser lift-off, peeling
occurs between the growth substrate 80 and the semiconductor
stacked body 10, and does not occur between the first electrode 30
and the first bonding layer 41. Furthermore, there is no
degradation of the surface of the first electrode 30.
Next, as shown in FIG. 5C, a protective film 60 is formed so as to
cover the semiconductor stacked body 10, the first electrode 30,
the intermediate metal film 50, and the first bonding layer 41. The
protective film 60 serves to reduce leakage and to protect the
element. The protective film 60 is formed by sputtering, for
instance. The film thickness of the protective film 60 is
illustratively 100 nm or more and 400 nm or less. The protective
film 60 is illustratively made of insulator.
Next, as shown in FIG. 6A, the protective film 60 is selectively
removed. More specifically, the protective film 60 on the first
major surface 10a of the semiconductor stacked body 10 is
selectively etched and removed. Then, a second electrode 20 is
formed on the first major surface 10a of the semiconductor stacked
body 10 exposed by the removal of the protective film 60. The
second electrode 20 is illustratively a multilayer metal film of
Ti/Pt/Au. The film thickness of Ti is illustratively 20 nm. The
film thickness of Pt is illustratively 50 nm. The film thickness of
Au is illustratively 700 nm. The second electrode 20 is formed by
evaporation, for instance.
Subsequently, as shown in FIG. 6B, the support substrate 70 is cut
(diced) along a dicing line DL. Thus, as shown in FIG. 6C, a
semiconductor light emitting element 110 as a single chip is
formed. In such a manufacturing method, no peeling occurs between
the first electrode 30 and the first bonding layer 41 when the
growth substrate 80 is removed by laser lift-off. Thus, the
semiconductor light emitting element 110 having high reliability
can be manufactured with high yield.
Third Embodiment
FIGS. 8A and 8B are schematic cross-sectional views describing an
example structure of a semiconductor light emitting element
according to a third embodiment.
FIG. 8A is a schematic cross-sectional view describing the overall
structure of a semiconductor light emitting element 120.
FIG. 8B is a schematic cross-sectional view enlarging the portion A
in FIG. 8A.
As shown in FIG. 8A, the semiconductor light emitting element 120
according to the third embodiment includes a support substrate (a
conductive substrate) 70, a bonding portion 40 provided on the
support substrate 70, an intermediate metal film 50 provided on the
bonding portion 40, a first electrode 30 provided on the
intermediate metal film 50, a semiconductor stacked body 10
provided on the first electrode 30, and a second electrode 20
provided on the semiconductor stacked body 10.
A side surface of the semiconductor stacked body 10 is slanted. A
first major surface 10a of the semiconductor stacked body 10 has a
smaller area than a second major surface 10b of the semiconductor
stacked body 10.
A protective film 60 is formed so as to cover a part of a first
major surface 10a of the semiconductor stacked body 10, a side
surface of the semiconductor stacked body 10, and a part of upper
surface of the first bonding layer 41.
The semiconductor light emitting element 120 according to the third
embodiment is different from the semiconductor light emitting
element 110 according to the first embodiment in that the first
bonding layer 41 in the bonding portion 40 is in contact with at
least an end surface 30b of the first electrode 30. The end surface
30b is also called a side surface or an edge surface.
Here, as shown in FIG. 8B, the first bonding layer 41 is a metal
multilayer film of bonding metal films 411, 412, 413, and 414. In
this metal multilayer film, the bonding metal film 414 is resistant
to etching for the semiconductor stacked body 10. Furthermore, the
bonding metal film 414 is in contact with at least the end surface
30b of the first electrode 30. The bonding metal film 414
illustrated in FIG. 8B is further in contact with the major surface
50a of the intermediate metal film 50, the second major surface 10b
of the semiconductor stacked body 10, and the major surface 60a of
the protective film 60.
The bonding metal film 414 is illustratively made of Ni. Because
the end surface 30b of the first electrode 30 is covered with the
bonding metal film 414 from the major surface 30a of the first
electrode 30, the metal film of the first electrode 30 is protected
during the manufacturing process. The bonding metal film 414 is
resistant to etching for the semiconductor stacked body 10. Hence,
the bonding metal film 414 functions as an etching stopper when the
semiconductor stacked body 10 is etched during the manufacturing
process.
With the bonding metal film 414 functioning as an etching stopper,
unwanted etching can be suppressed during the etching of the
semiconductor stacked body 10. Unwanted etching causes the etched
portion to fly as dust. If metal is turned to dust, the dust is
attached to the semiconductor light emitting element and causes
leakage current. The semiconductor light emitting element 120
according to this embodiment can suppress the occurrence of leak
current.
Fourth Embodiment
An example method for manufacturing a semiconductor light emitting
element according to a fourth embodiment is described.
FIGS. 9A to 11D are schematic cross-sectional views sequentially
describing an example process for manufacturing a semiconductor
light emitting element 120.
In this embodiment, a substrate illustratively made of sapphire is
used as a growth substrate 80 for growing a semiconductor stacked
body 10.
First, as shown in FIG. 9A, a semiconductor stacked body 10 is
formed on the growth substrate 80. The thickness of the growth
substrate 80 is illustratively 300-500 micrometers (.mu.m). The
semiconductor stacked body 10 is formed on the growth substrate 80
by epitaxial growth.
Next, a first electrode 30 is formed on the semiconductor stacked
body 10. The first electrode 30 is illustratively a multilayer
metal film of electrode metal films 310 and 320. Subsequently, an
intermediate metal film 50 is formed on the first electrode 30. The
first electrode 30 and the intermediate metal film 50 are formed by
sputtering or CVD (chemical vapor deposition), for instance.
Next, as shown in FIG. 9B, the semiconductor stacked body 10, the
first electrode 30, and the intermediate metal film 50 are
selectively etched and divided on the growth substrate 80. The
division is performed for each chip. By way of example, FIG. 9B
shows a divided state corresponding to three chips. The etching
process may be either dry etching or we etching. Alternatively, the
division may be performed by laser processing.
Next, as shown in FIG. 9C, a first bonding layer 41 is formed so as
to cover the divided first electrode 30 and intermediate metal film
50 from above. The first bonding layer 41 is illustratively a
multilayer metal film of bonding metal films 414, 411, 412, and
413. Here, the bonding metal film 414 is formed in contact with at
least the end surface 30b of the first electrode 30. The bonding
metal film 414 illustrated in FIG. 9C is formed on the major
surface 50a and the end surface 50b of the intermediate metal film
50, the end surface 30b of the first electrode 30, and the second
major surface 10b of the semiconductor stacked body 10.
Next, as shown in FIG. 9D, a support substrate 70 with a second
bonding layer 42 provided thereon is prepared. Then, the second
bonding layer 42 is brought into face-to-face contact with the
first bonding layer 41. Thus, the semiconductor stacked body 10,
the first electrode 30, the intermediate metal film 50, and the
bonding portion 40 (first bonding layer 41, second bonding layer
42) are sandwiched between the growth substrate 80 and the support
substrate 70.
Then, heating treatment or ultrasonic treatment is performed to
cause interdiffusion between the first bonding layer and the second
bonding layer 42, thereby bonding them together. More specifically,
with the first bonding layer 41 and the second bonding layer 42
opposed to each other, a load of e.g. 5 kgf/cm.sup.2 or more and
500 kgf/cm.sup.2 or less is applied thereto, and they are heated to
e.g. 200.degree. C. or more and 400.degree. C. or less. This causes
interdiffusion between the first bonding layer 41 and the second
bonding layer 42, thereby forming a bonding portion 40. Thus, the
semiconductor stacked body 10 and the support substrate 70 are
bonded. The support substrate 70 also functions as a heat sink, for
instance. Here, the first electrode 30 and the intermediate metal
film 50 are interposed between the semiconductor stacked body 10
and the bonding portion 40.
Next, as shown in FIG. 10A, laser lift-off (LLO) is performed to
remove the growth substrate 80 from the semiconductor stacked body
10. Laser light 75 is produced using, for instance, an ArF laser
(wavelength 193 nm), KrF laser (wavelength 248 nm), XeCl laser
(wavelength 308 nm), or XeF laser (wavelength 353 nm).
The laser light 75 is transmitted through the growth substrate 80
to the semiconductor stacked body 10. Here, at the interface
between the growth substrate 80 and the semiconductor stacked body
10, the semiconductor stacked body 10 absorbs the energy of the
laser light 75. Thus, the III-V nitride components e.g. GaN in the
semiconductor stacked body 10 is thermally decomposed as shown in
the following reaction formula. GaN.fwdarw.Ga+1/2N.sub.2.uparw.
Consequently, as shown in FIG. 10B, the growth substrate 80 is
removed from the semiconductor stacked body 10.
In the manufacturing process according to this embodiment, the
intermediate metal film 50 is provided between the first electrode
30 and the first bonding layer 41. Hence, there is a sufficient
adhesion strength between the first electrode 30 and the first
bonding layer 41. This adhesion strength is sufficiently higher
than the adhesion strength between the growth substrate 80 and the
semiconductor stacked body 10 after irradiation with laser light
75. Hence, when the growth substrate 80 is removed by laser
lift-off, peeling occurs between the growth substrate 80 and the
semiconductor stacked body 10, and does not occur between the first
electrode 30 and the first bonding layer 41.
Next, as shown in FIG. 10C, a mask material M such as resist is
provided on the semiconductor stacked body 10, and the
semiconductor stacked body 10 is etched at the position between the
chips, so as to a side surface of the semiconductor stacked body 10
is tapered. The etching is performed by RIE (reactive ion etching),
for instance.
The etching of the semiconductor stacked body 10 proceeds from the
first major surface 10a. When the etching reaches the bonding metal
film 414 of the first bonding layer 41, the bonding metal film 414
serves as an etching stopper film. The bonding metal film 414 has a
sufficient etching selection ratio with respect to the
semiconductor stacked body 10. Thus, the etching of the
semiconductor stacked body 10 stops at the position of the bonding
metal film 414.
Furthermore, the bonding metal film 414 is in contact with the end
surface 30b of the first electrode 30. Hence, during the etching of
the semiconductor stacked body 10, the end surface 30b of the first
electrode 30 is protected by the bonding metal film 414, and can be
prevented from being etched. Thus, the manufacturing process
according to this embodiment suppresses the occurrence of metal
dust during the etching of the semiconductor stacked body 10.
Hence, the occurrence of leak current can be suppressed in the
completed semiconductor light emitting element.
Next, as shown in FIG. 11A, a protective film 60 is formed on the
semiconductor stacked body 10. The protective film 60 serves to
reduce leakage and to protect the element. The protective film 60
is formed by sputtering, for instance. The film thickness of the
protective film 60 is illustratively 100 nm or more and 400 nm or
less.
Next, as shown in FIG. 11B, the protective film 60 is selectively
removed. More specifically, the protective film 60 on the first
major surface 10a of the semiconductor stacked body 10 is
selectively etched and removed. Then, a second electrode 20 is
formed on the first major surface 10a of the semiconductor stacked
body 10 exposed by the removal of the protective film 60. The
second electrode 20 is illustratively a multilayer metal film of
Ti/Pt/Au. The film thickness of Ti is illustratively 20 nm. The
film thickness of Pt is illustratively 50 nm. The film thickness of
Au is illustratively 700 nm. The second electrode 20 is formed by
evaporation, for instance.
Subsequently, as shown in FIG. 11C, the support substrate 70 is cut
(diced) along a dicing line DL. Thus, as shown in FIG. 11D, a
semiconductor light emitting element 120 as a single chip is
formed. In such a manufacturing method, peeling is suppressed
between the first electrode 30 and the first bonding layer 41 when
the growth substrate 80 is removed by laser lift-off. Furthermore,
the occurrence of leak current due to metal dust is suppressed.
Thus, the semiconductor light emitting element 120 having high
reliability can be manufactured with high yield.
Fifth Embodiment
FIG. 12 is a schematic cross-sectional view describing an example
configuration of a semiconductor light emitting device according to
a fifth embodiment.
The semiconductor light emitting device 200 includes a
semiconductor light emitting element 110 (120), a molded body 210
enclosing the semiconductor light emitting element 110 (120), and
terminals 220 being in electrical continuity with the semiconductor
light emitting element 110 (120) and provided outside the molded
body 210.
The chip-shaped semiconductor light emitting element 110 (120) is
mounted on a die 215. The semiconductor light emitting element 110
(120) is mounted on the die 215 via a metal film provided on the
support substrate 70 side. This brings the first electrode 30 of
the semiconductor light emitting element 110 into electrical
continuity with the die 215.
The die 215 is in electrical continuity with one terminal 220a. The
second electrode 20 of the semiconductor light emitting element 110
(120) is connected to the other terminal 220b via a connecting wire
W such as a bonding wire. The terminals 220 (220a and 220b) extend
outside from the side surface of the molded body 210, for instance,
and are bent from the side surface to the rear surface along the
outline of the molded body 210.
The semiconductor light emitting device 200 is of the SMD (surface
mount device) type.
The molded body 210 is a packaging member enclosing the
semiconductor light emitting element 110 (120), the die 215, and
part of the terminals 220. In the molded body 210, the emission
surface side 210a for light emission is translucent. If necessary,
the emission surface side 210a of the molded body 210 is provided
with phosphor.
The semiconductor light emitting device 200 is mounted on a
substrate S. On the rear surface side of the molded body 210, the
terminals 220 (220a and 220b) of the semiconductor light emitting
device 200 are bonded with solder to pads PD provided on the
substrate S. Thus, the semiconductor light emitting device 200 is
mechanically fixed onto the substrate S, and electrically connected
to a circuit (not shown) provided on the substrate S.
Such a semiconductor light emitting device 200 is operable to emit
light with high reliability because the semiconductor light
emitting element 110 (120) according to the embodiments is used
therein.
It is noted that the semiconductor light emitting device 200 is
also applicable to any type other than the SMD type.
The embodiments of the invention have been described. However, the
invention is not limited to these examples.
For instance, in the semiconductor light emitting element 110
(120), the intermediate metal film 50 may be provided as the
lowermost layer of the first electrode 30. Alternatively, the
intermediate metal film 50 may be provided as the uppermost layer
of the bonding portion 40.
Furthermore, for instance, an electronic circuit capable of
processing light signals emitted from the semiconductor light
emitting element 110 (120) can be integrated on the same support
substrate 70 to form an optoelectronic integrated circuit. Such an
optoelectronic integrated circuit is also encompassed in the
embodiments.
Furthermore, the components of the above embodiments can be
combined with each other as long as technically feasible, and such
combinations are also encompassed within the scope of the invention
as long as they include the features of the invention.
Furthermore, those skilled in the art can conceive various
modifications and variations within the spirit of the invention,
and it is understood that such modifications and variations are
also encompassed within the scope of the invention.
While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to
limit the scope of the inventions. Indeed, the novel embodiments
described herein may be embodied in a variety of other forms;
furthermore, various omissions, substitutions and changes in the
form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
invention.
* * * * *